modularize hosts function

flake.nix

@@ -2,10 +2,12 @@
   inputs.nixpkgs.url = "nixpkgs/nixos-21.05";
   inputs.unstable.url = "nixpkgs/nixos-unstable";
 
-  outputs = { self, unstable, nixpkgs }: {
-    nixosModule = { ... }: {
-      imports = [ ./. ];
+  outputs = { self, ... }@inputs:
+    {
+      nixosModule = { ... }: { imports = [ ./. ]; };
+
+      nixosConfigurations = self.lib.getHosts inputs ./hosts;
+
+      lib.getHosts = import lib/hosts.nix;
     };
-    nixosConfigurations = import ./hosts { modules = [ ./. ]; inherit unstable nixpkgs; };
-  };
 }

hosts/default.nix

@@ -1,35 +0,0 @@
-{ modules, nixpkgs, unstable }:
-let
-
-  hostMetadata =
-    let
-      fs = builtins.readDir ./.;
-      inherit (builtins) concatMap attrNames;
-      hostNames = concatMap (x: if fs.${x} == "directory" then [ x ] else [ ]) (attrNames fs);
-    in
-    builtins.listToAttrs (map
-      (hn: { name = hn; value = import (./. + "/${hn}"); })
-      hostNames);
-
-  hardwareModule = hardware: (
-    {
-      qemu = (x: { imports = [ "${x.modulesPath}/profiles/qemu-guest.nix" ]; });
-      physical = (x: { imports = [ "${x.modulesPath}/installer/scan/not-detected.nix" ]; });
-    }
-  ).${hardware};
-
-in
-builtins.mapAttrs
-  (n: v:
-    let pkgs = { inherit nixpkgs unstable; }.${v.pkgs};
-    in
-    pkgs.lib.nixosSystem {
-      inherit (v) system;
-      modules = modules ++ [
-        (./. + "/${n}/configuration.nix")
-        (hardwareModule v.hardware)
-        ({ ... }: { networking.hostName = n; })
-      ];
-    }
-  )
-  hostMetadata

hosts/dev-cli/configuration.nix

@@ -3,4 +3,6 @@
   services.qemuGuest.enable = true;
   sconfig.profile = "server";
   services.getty.autologinUser = "root";
+  fileSystems."/" = { device = "/dev/vda1"; fsType = "ext4"; };
+  boot.loader.grub.device = "nodev";
 }

hosts/dev-cli/default.nix

@@ -2,4 +2,5 @@
   pkgs = "unstable";
   system = "x86_64-linux";
   hardware = "qemu";
+  module = ./configuration.nix;
 }

hosts/dev-gui/configuration.nix

@@ -4,4 +4,6 @@
   sconfig.profile = "desktop";
   sconfig.gnome = true;
   services.getty.autologinUser = "root";
+  fileSystems."/" = { device = "/dev/vda1"; fsType = "ext4"; };
+  boot.loader.grub.device = "nodev";
 }

hosts/dev-gui/default.nix

@@ -2,4 +2,5 @@
   pkgs = "unstable";
   system = "x86_64-linux";
   hardware = "qemu";
+  module = ./configuration.nix;
 }

hosts/hp/default.nix

@@ -2,4 +2,5 @@
   pkgs = "nixpkgs";
   system = "x86_64-linux";
   hardware = "physical";
+  module = ./configuration.nix;
 }

hosts/lenny/default.nix

@@ -2,4 +2,5 @@
   pkgs = "nixpkgs";
   system = "x86_64-linux";
   hardware = "physical";
+  module = ./configuration.nix;
 }

hosts/neo/default.nix

@@ -2,4 +2,5 @@
   pkgs = "nixpkgs";
   system = "x86_64-linux";
   hardware = "physical";
+  module = ./configuration.nix;
 }

hosts/tosh/default.nix

@@ -2,4 +2,5 @@
   pkgs = "nixpkgs";
   system = "x86_64-linux";
   hardware = "physical";
+  module = ./configuration.nix;
 }

lib/hosts.nix

@@ -0,0 +1,31 @@
+callerInputs: hostsPath:
+let
+
+  hostMetadata = builtins.mapAttrs
+    (name: _: import (hostsPath + "/${name}"))
+    (builtins.readDir hostsPath);
+
+  hardwareModules =
+    {
+      physical = (x: { imports = [ "${x.modulesPath}/installer/scan/not-detected.nix" ]; });
+      vmware = (x: { virtualisation.vmware.guest.enable = true; });
+      qemu = (x: {
+        services.qemuGuest.enable = true;
+        imports = [ "${x.modulesPath}/profiles/qemu-guest.nix" ];
+      });
+    };
+
+  getHostConfig = hostName: hostMeta:
+    callerInputs.${hostMeta.pkgs}.lib.nixosSystem
+      {
+        inherit (hostMeta) system;
+        modules = [
+          (callerInputs.self.nixosModule)
+          (hostMeta.module)
+          (hardwareModules.${hostMeta.hardware})
+          (_: { networking.hostName = hostName; })
+        ];
+      };
+
+in
+builtins.mapAttrs getHostConfig hostMetadata